My problem wasn't so much slipping when walking, but slipping when pedaling.... so the pontoons wouldn't help as much.

My primary problem was slipping while on the pedal, usually when I'm starting from a red light with cabs and buses honking behind me. I don't always have time to flip the pedal over and clip in before having to get across an intersection. The rubber on the bottom allows me to start pedaling with my right leg clipped in and keep my left leg safely planted on the pedal until I'm moving and can find the clip.